Maslinic acid and ration size enhanced hepatic protein‐turnover rates of gilthead sea bream (Sparus aurata)

Maslinic acid (MA) is a natural triterpene that can be used as an additive in the diet of trout. We investigated the effects of feeding with MA and a fixed ration (10 g kg^?1 body weight) with respect to growth, protein‐turnover rates and nucleic‐acid concentration in the liver of gilthead sea bream grown under fish‐farm conditions. Five groups of 12 g of a mean body mass were fed for 210 days with diets containing 0 (control), 0.05 and 0.1 g of MA per kg of diet. Two groups were fed ad libitum (control AL and MA₁₀₀AL), and three with a fixed ration (control R, MA₅₀R and MA₁₀₀R). At the end of the experiment, higher body weights, liver weight, feed‐efficiency and PER were found in MA₁₀₀AL and MA₁₀₀R fish. Fractional and absolute protein‐synthesis rates in liver of MA₁₀₀R fish were higher than in the control, resulting in a higher absolute protein‐accumulation rate and tissue growth. Total DNA content in MA₁₀₀AL and MA₁₀₀R was higher than in control. Studies of light and electron microscopy corroborated these results. These findings indicate that MA added to the diet can stimulate growth, hepatic protein‐turnover rates and tissue hyperplasia in gilthead sea bream.